The present invention relates to a method of forming a resist pattern of a thin-film device or a thick-film device, a frame plating method for a thin-film device or a thick-film device, and a method of manufacturing a thin-film magnetic head.
Japanese patent publication Nos. 10073927A and 11204399A disclose a fine pattern forming method called as xe2x80x9cRELACExe2x80x9d used in a fabrication of a semiconductor device.
This known method makes it possible to reduce the resist hole diameter and the separating width of a resist pattern by covering a resist pattern containing a material generating acid by exposure with a fine pattern-forming material containing a material cross-linked in the presence of acid, by mixing-baking or exposing them to generate acid in the resist pattern, and by forming a cross-linked layer generating on the interface as a covering layer of the resist pattern to thicken the resist pattern.
According to the known method, since the fine pattern-forming material is composed of a mixture of a water-soluble resin and a water-soluble cross-linking agent, it is very difficult to lower the mixing-baking temperature. Definitely, the mixing-baking temperature is lowered if concentrations of the water-soluble cross-linking agent is increased. However, if the concentrations of the water-soluble cross-linking agent is increased, cross-linking at room temperature between the water-soluble resin and the water-soluble cross-linking agent will progress causing the fine pattern-forming material preserved at roan temperature to become chemically unstable.
Particularly, in case that this known method is applied to a fabrication of a thin-film device or a thick-film device which use thick resist films, it is difficult to always form a highly precise resist pattern. This is because since heating is required twice for such the thick resist pattern at the high mixing-baking temperature of 105xc2x0 C. or more, the resist pattern itself will deform due to the applied heat. This tendency of deformation is strong in a high-resolution resist material because it will have a lower heat resistance.
Japanese patent publication No. 10073927A discloses that the fine pattern-forming material may contain only a water-soluble cross-linking agent. However, since such cross-linking agent has a low molecular weight and thus a resist pattern made of the cross-linking agent only will become thin and will not so shrink, desired reduction of the resist hole diameter and the separating width of the resist pattern by the cross-linking will not be expected. Therefore, when performing the known method, it is necessary to use a mixture of a water-soluble resin and a water-soluble cross-linking agent as the fine pattern-forming material.
It is therefore an object of the present invention to provide a resist pattern forming method, a frame plating method using a resist pattern formed by the method, and a method of manufacturing a thin-film magnetic head, whereby a fine and high-resolution resist pattern can be stably formed.
According to the present invention, a method of forming a resist pattern includes a step of forming a resist pattern on a substrate or on a layer formed on a substrate using a resist material containing a material generating acid by exposure or heating, a step of coating only a water-soluble cross-linking agent on the resist pattern, the water-soluble cross-linking agent being cross-linked in the presence of acid, a step of coating a resin material containing at least a water-soluble resin on the water-soluble cross-lining agent, and a step of exposing or heating the resist pattern to generate acid from the resist pattern, a cross-linking reaction of the water-soluble cross-liking agent being occurred in the presence of the generated acid to form a covering layer over the resist pattern.
A frame plating method according to the present invention includes a step of plating a pattern using the resist pattern with the covering layer formed by the above-mentioned resist pattern forming method as a frame, and a step of removing the resist pattern with the covering layer. In a manufacturing method of a thin-film magnetic head according to the present invention, a magnetic pole is plated by the above-mentioned frame plating method.
The water-soluble cross-linking agent and the water-soluble resin are independently prepared and coated in isolation. Thus, the water-soluble cross-linking agent and the water-soluble resin can be kept in the stable state without inducing room-temperature cross-linking reaction until they are coated and thus partially mixed. Of course, sufficient polymerization can be expected. Therefore, even when a fine resist pattern of a thin-film device or a thick-film device, with a large thickness, is to be formed, a good cross-linking reaction can be generated even at a low mixing-baking temperature. Thus, a highly precise resist pattern without the distortion by heat can be stably obtained. In addition, a resist material providing a high resolution but having a low heat-resistance can be used. Consequently, a more fine and highly precise resist pattern can be stably obtained.
It is preferred that the resin material containing at least a water-soluble resin consists of only a water-soluble resin, or that the resin material containing at least a water-soluble resin consists of a water-soluble resin and a water-soluble cross-linking agent with a low concentration.
It is also preferred that the method further includes a step of partially removing the water-soluble cross-linking agent by centrifugal force after coating only the water-soluble cross-linking agent on the resist pattern.
It is preferred that the method further includes a step of entirely exposing a surface of the formed resist pattern before coating the water-soluble cross-linking agent on the resist pattern, and/or a step of performing a surface treatment of the formed resist pattern by using an acid liquid or an acid gas before coating the water-soluble cross-linking agent on the resist pattern.